Female indices were measured on six soybean cultivars with resistance to Heterodera glycines derived from PI 88788. Cultivars were inoculated with four isolates of race 6, 3 of race 9, 2 of race 4, and one of race 14. Changes in female index from slightly < or > 10% of the test cultivars compared to 'Lee' resulted in a change of most of the race designations after at least three generations on ...

Population development of isolates of Heterodera lespedezae from Illinois and North Carolina was compared on Korean, sericea, and striate lespedezas and red clover at soil temperatures of 14, 18, 22, 26, 30, 34 C (+/- 1 C) and in a greenhouse where temperatures ranged from 19 to 40 C (av. 25 C). Cyst production on all plants, but not at all temperatures, was significantly different between the ...

The effects of root diffusates of selected plants within the families Chenopodiaceae and Cruciferae and the hatching agent zinc chloride were tested for their effects on hatching and emergence of juveniles from cysts of Heterodera schachtii and a race of H. trifolii parasitic on Chenopodaceae and Cruciferae in The Netherlands. Although all diffusates strongly stimulated hatching of juveniles of...

The duration of effectiveness of a foliar spray of oxamyl against Heterodera schachtii and the location of the protective effect were determined by applying a foliar spray at 0.04 kg (a.i.)/100 liters of water to cabbage seedlings. Oxamyl, or a metabolite of oxamyl, apparently is translocated to anti becomes prolective in the root within 7 days. Between 7 and 14 days, the location of the protec...

A total of 62 populations of Heterodera glycines were collected in 10 states along the Mississippi and Missouri rivers, and 206 populations were collected in Arkansas. Among the 62 populations, races 2, 3, 4, 5, 6, 9, and 14 were found south of 37 degrees N latitude, and races 1 and 3 were found north of 37 degrees N latitude. In Arkansas samples, races 2, 4, 5, 6, 9, and 14 comprised 87% of th...

Experiments were conducted to determine the relationship between time of infection by Heterodera glycines and soybean growth in the greenhouse and yield of plants grown in the field. Soybean cultivar Essex seedlings growing in the greenhouse were inoculated with H. glycines at 2, 4, or 6 weeks after planting. Seedling growth was inhibited by H. glycines infection at 2 or 4 weeks after planting ...

Alternate planting dates and periodic destruction of the previous year's soybean crop as well as 1-year bare fallow were used to establish a range of population densities ofHeterodera glycines for the subsequent year. Soybean cultivar Coker 156 (susceptible, moderately tolerant) was compared to cultivars Essex (susceptible, intolerant) and Bedford (resistant) to evaluate tolerance at different ...

Effects of tannic acid on hatching of Heterodera glycines eggs were determined in vitro using three batches of eggs obtained from greenhouse cultures in Florida or from naturally infested field soil in Minnesota. A quadratic model fits the percentage egg hatch. Hatch increased with increasing tannic acid concentrations from 0 to about 39 mg/liter, then declined with further increases in concent...

A method of selecting soybean cyst nematode (Heterodera glycines Ichinohe) on segregating soybean progeny was evaluated for developing a population capable of reproducing on PI 437654. Direct selection on PI 437654 was not possible, since no cysts developed on it. Cysts were selected for 12 nematode generations on F and F plants of Forrest x PI 437654. No cysts of the selected population were p...

Isolates from a race 5 field population of Heterodera glycines were cultured separately on soybean cultivars 'Bedford' (resistance derived from Peking and plant introduction [PI] 88788) and 'Cordell' (resistance derived from 'Peking', PI 88788, and PI 90763) for 10, 12, and 14 generations. Reproduction was measured of the 10th, 12th, and 14th generations on Bedford and Cordell and on Peking, 'P...